P2797 on 2009-2013 Cadillac Escalade ESV Hybrid: Aux Pump Circuit Causes & Fixes

What's Unique About the 2009-2013 Cadillac ESCALADE ESV

This issue is specific to the Cadillac Escalade and its platform mates (Tahoe, Yukon, Silverado, Sierra) with the Two-Mode Hybrid system (RPO HP2) and its 2ML70 transmission. General Motors issued a Technical Service Bulletin (PIP4873A) because this code frequently leads to the incorrect diagnosis and replacement of the auxiliary transmission pump. The bulletin clarifies that the root cause is far more likely to be a wiring issue between the control modules, a known failure point on this platform.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• Check Engine Light or "Service Hybrid System" message is illuminated
• Vehicle fails to enter "Auto-Stop" (engine does not shut off at stops)
• Jerking or bumping sensation when the vehicle switches between electric and gasoline engine power
• A lull or slip followed by a kick or grab during acceleration from a stop.
• Harsh, delayed, or erratic shifting
• Reduced acceleration or feeling of power loss
• In severe cases, the transmission may seem to slip or fail to engage a gear
• Audible clicking noises from the transmission area, associated with the pump stalling.

Most Likely Causes

1. Damaged Wiring Harness or Connectors 🔴 High Probability As identified in TSB PIP4873A, the wiring between the Hybrid Powertrain Control Module (HPCM) and the Auxiliary Transmission Fluid Pump Control Module is a known weak point. Wires can chafe, corrode, or break, and pins can back out of connectors, causing a loss of communication or high resistance.
   How to confirm: Visually inspect the entire harness between the HPCM and the pump control module for damage. A forum user specifically identified the connectors located under the battery as a source of high resistance and overheating. Perform continuity, resistance, and voltage drop tests on the circuits as outlined in the factory service manual and TSB PIP4873A.
   Typical fix: Repair the damaged section of the wiring harness or replace the affected connector pigtail. In some cases, simply cleaning corroded or overheated connector pins and ensuring a secure connection can resolve the issue.
   Est. part cost: $20-$100
2. Faulty Auxiliary Transmission Fluid Pump Control Module 🟡 Medium Probability This module controls the pump's operation. Forum discussions and service information suggest it can fail, sometimes due to high current causing poor connections at its pins. It should be suspected after wiring is confirmed to be intact, as per GM's diagnostic flow. TSB PIP4833E notes that if the module has a date code of 089-11-XXXX or older, it is a candidate for replacement if the concern is intermittent and cannot be reproduced.
   How to confirm: After verifying the wiring is good, diagnosis with a GM-specific scan tool is required to check module status and communication. The module itself may report internal faults to the HPCM. TSB PIP4833E notes that if the module has a date code of 089-11-XXXX or older, it is a candidate for replacement if the concern is intermittent and cannot be reproduced.
   Typical fix: Replace the Auxiliary Transmission Fluid Pump Control Module. The replacement part is GM P/N 24261817. Note that this part may require programming or special setup procedures, though forum users report it does not. For 2009 models, adapter harnesses are required.
   Est. part cost: $150-$300

Rare But Worth Checking

• Failed Auxiliary Transmission Fluid Pump: This is a rare cause for this specific code. TSB PIP4873A explicitly warns *not* to replace the pump if code P0C2B is present with or without P2797, as the fault is almost always in the wiring or control module. Only replace the pump if all wiring and module diagnostics have passed and the pump itself is proven to be faulty through specific diagnostic tests.

Diagnosis Steps

1. Scan the vehicle for all Diagnostic Trouble Codes (DTCs). Note if P2797 is accompanied by P0C2B or P0AC4.
2. Strictly follow the diagnostic procedure outlined in TSB #PIP4873A.
3. DO NOT replace the auxiliary transmission fluid pump if P0C2B is present.
4. Thoroughly inspect the wiring harness and connectors between the Hybrid Powertrain Control Module (HPCM) and the Auxiliary Transmission Fluid Pump Control Module. Look for any signs of chafing, corrosion, loose pins, or breaks.
5. A forum member noted that on their '09 model, the high-current connectors located under the battery were a source of high resistance and overheating, which was resolved by cleaning them thoroughly.
6. Inspect for backed-out or loose-fitting terminals on both ends of the harness.
7. If the visual inspection reveals no damage, use a digital multimeter to test the integrity of the power, ground, and signal wires according to the factory service manual specifications.
8. If all wiring and connections test normal, further diagnosis of the Auxiliary Transmission Fluid Pump Control Module is required. Check the module's date code; if it's from 2011 or earlier (089-11-XXXX or older), it's a higher suspect for intermittent issues.
9. Only consider replacing the auxiliary pump itself as a last resort after all other possibilities have been definitively ruled out.

Parts You'll Likely Need

• Auxiliary Transmission Fluid Pump Control Module (OEM #24261817) — This module is the second most likely cause after wiring issues. It controls the pump and communicates with the HPCM. This part supersedes several previous numbers, including 29547550, 29546636, 29546469, 29546431, and 29543906.
  Trusted brands: ACDelco / GM Genuine Parts
  OEM price range: $120-$300
  Aftermarket price range: $100-$200
• Wiring Harness Pigtail Connector — If the connector at the module or HPCM is corroded or damaged, a pigtail is used to repair the harness without replacing the entire loom.
  Trusted brands: ACDelco, Dorman
  OEM price range: $30-$60
  Aftermarket price range: $20-$40

Related Codes That Often Appear With This One

• P0C2B — This code, 'Auxiliary Transmission Fluid Pump Control Module Feedback Signal', is often set with P2797. TSB PIP4873A directly addresses both codes, indicating they point to the same wiring or control module fault, not a pump failure. P0C2B sets when the HPCM doesn't receive a diagnostic signal from the pump module for 1.5 seconds.
• P0AC4 — This code, 'Hybrid Powertrain Control Module Requested MIL Illumination', is a general code indicating that the hybrid control module has detected a fault (like P2797) and has requested the Check Engine Light to be turned on.
• P079A — This code, 'Transmission Friction Element Slip Detected', can sometimes accompany P2797 and P0C2B, indicating a slipping clutch, which can be a symptom of the low hydraulic pressure caused by the auxiliary pump issue.

Technical Service Bulletins (TSBs) & Recalls

• PIP4873A: States that DTC P2797 with or without P0C2B is not likely caused by the auxiliary transmission fluid pump and instructs technicians to inspect wiring between the HPCM and the pump control module. If wiring is OK, suspect the control module.
• PIP4833E: Details the parts restriction program for the auxiliary pump and control module, requiring TAC authorization for ordering to prevent unnecessary replacement of parts due to misdiagnosis. Also notes adapter harnesses are needed for 2009 models.

Platform-Specific Known Issues

• GM issued TSB #PIP4873A specifically for the 2009-2013 Hybrid trucks and SUVs to address the common misdiagnosis of P2797 and P0C2B, directing technicians to focus on wiring and the control module instead of the pump.
• GM also issued TSB #PIP4833E, which placed the Auxiliary Transmission Fluid Pump and its Control Module under a parts restriction, requiring technicians to contact the GM Technical Assistance Center (TAC) before ordering to verify the diagnosis was performed correctly. This underscores the high rate of misdiagnosis.

Scan Tool Commands That Help

• GDS2 (GM Global Diagnostic System 2): Vehicle Diagnosis > Vehicle Communication Diagnostics > Network Communication Status — This function is used to verify which control modules are communicating on the CAN bus. For P2797/P0C2B, it's a primary step to confirm if the Auxiliary Transmission Fluid Pump Control Module is offline or has intermittent communication with the HPCM, which points towards a wiring or module fault.

Wiring & Ground Locations

• Drive Motor Generator Power Inverter Module — Located on the right side of the engine compartment.. This module assembly contains the control logic that operates the auxiliary transmission fluid pump. The wiring between this unit and the pump control module is a primary area of concern.
• G100 — Ground point located at the right front of the engine compartment.. A poor ground at this location can cause a variety of electrical issues for components in the engine bay. It should be checked for corrosion and tightness during any electrical diagnosis.
• G201 — Ground point located at the left end of the instrument panel / dashboard.. This is a key interior ground point. While less likely to be the direct cause, verifying major grounds is a best practice when chasing intermittent electrical faults.
• Transmission 16-Way and 24-Way Connectors — These are the main electrical pass-through connectors for the internal transmission wiring harness.. These connectors are critical points of failure. A problem here can interrupt signals for multiple transmission components, including the auxiliary pump system.

Real Owner Repair Stories

• Tahoe Yukon Forum user 'ChuckC' (GMC Yukon Hybrid (same 2ML70 platform)) — Jerking sensation when switching between hybrid and engine modes, pauses in acceleration, sudden accelerations at low speeds. Codes P2797, P0C2B, and P0AC4 were present.
  ❌ Tried (didn't work) The user went straight for the recommended TSB fix; no other failed attempts were mentioned.
  ✅ What actually fixed it Replaced the auxiliary transmission fluid pump control module (GM P/N 24261817) and two associated harnesses (P/N 24259589 and 24259590). The total cost for parts and labor was $637.

OEM Part Supersession History

• 29543906, 29546431, 29546469, 29546636, 29547550 → 24261817 — Part revision and consolidation by the manufacturer.
  Heads up: CRITICAL: For 2009 models, replacing the original module with the current P/N 24261817 requires ordering two adapter harnesses, P/N 24259589 and 24259590, as stated in TSB PIP4833E. Failure to order these adapters will result in mismatched connectors. Note that P/N 24259590 has reportedly been discontinued and may be difficult to source.

Model Year Variations Within This Range

• 2009: The original Auxiliary Transmission Fluid Pump Control Module on 2009 (and 2008) models used different electrical connectors than the later replacement part (P/N 24261817). A service bulletin (PIP4833E) specifies that adapter harnesses (P/N 24259589 and 24259590) must be ordered and installed when replacing the module on these earlier model years to ensure compatibility.